Also, payment has to be received by 5pm (Western Standard Time)...

Also, payment has to be received by 5pm (Western Standard Time) on 31 December. If you pay by BPay you have to allow time for the payment to be processed by the bank, funds have to be received if the registry gets the payment by 5pm on that day. If you pay by the 29th you should be alright, even the 30th you may be ok depending on your bank. Good luck if you decide to BPay on the 31st. Being the Christmas/New Years period, payment processing may take a little longer than normal so make sure you allow for that if BPaying.